1. Field of the Invention
The present invention relates to a navigation system for providing real-time traffic information to users connected thereto through a communication network and to a traffic information processing method by such a navigation system.
2. Description of the Related Art
In general, a navigation system displays the current location of a moving object on a map shown in a display screen, that location being calculated using information received from Global Positioning System (hereinafter referred to as “GPS”). The navigation system also provides drivers with various navigation information required for driving by displaying a travel direction of the moving object, a distance to a destination to go to, the current travel speed of the moving object, a route set by the driver before driving, the best route to the destination and so forth. Such a navigation system (or GPS positioning system) is presently mounted to a variety of moving objects such as ships, air planes, vehicles, etc. and is widely used for confirming the current location and the current speed of the moving object or for determining the travel route. The navigation system, in particular, receives a radio wave indicating latitude, longitude, altitude and the like from a plurality of artificial satellites belonging to the GPS, calculates them, and then visually shows map information including the current location to the driver or audibly notifies the driver of that information.
A typical navigation system is realized in a form of one terminal. The typical navigation system has a storage medium such as a CD ROM (Compact Disc Read Only Memory) in which map data is stored and a GPS receiver for receiving GPS signals. This typical navigation system is very expensive, which imposes a heavy burden on users thereof. A recent navigation system, which has been developed in order to get rid of such an economic burden, is characterized in that it has a storage medium for storing map data and includes an information center which calculates an optimal travel route, creates route guidance data in accordance with the calculated result and provides that data to a subscriber when there is a demand for navigation function from the subscriber. The route guidance data created by the information center is provided to a mobile terminal such as a cellular phone through a communication network (e.g., wireless network) and is displayed on a display window (liquid crystal display) of the terminal.
On the other hand, the typical and the recent navigation systems have developed into a type reflecting real-time traffic information as well as providing the travel route information on the basis of the map data stored in the storage medium. The recent navigation system, for example, has a travel route server and a traffic information server in a server system such as an information center by which route guidance data for guiding an optimal travel route is created and the created data is provided to subscribers through a network.
In this navigation system which calculates the travel route reflecting the real-time traffic information, there is no problem when a format of map data for calculating the travel route is the same as that of map data for representing the traffic information. When either map data is converted or processed for upgrading, however, the user faces a serious situation in which it is impossible to calculate the optimal travel route reflecting the real-time traffic information unless the other map data is converted or processed for upgrading. Above all, this problem is incurred in a case when there exists one format of the map data for representing the traffic information and there exist plural formats of the map data for calculating the travel route like in a case when there is a single provider of the real-time traffic information and there are multiple providers of the map data for calculating the travel route.